1. Field
One or more exemplary embodiments of the present invention relate to an optical image modulator, an optical apparatus including the same, and methods of manufacturing and operating the optical image modulator.
2. Description of the Related Art
Optical image modulators are used in imaging systems such as a laser radar (LADAR) and an infrared (IR) camera. Optical image modulators receive optical information about an object, modulate the brightness of the optical information to vary wavelengths, and transmit the modulated optical information to an optical image sensor such as a charge-coupled device (CCD).
In particular, optical-electric-optical (OEO) image modulators refer to modulators that convert optical information into electrical information, modulate the electrical information, and convert the modulated electrical information into optical information. OEO image modulators may amplify optical information, modulate the optical information at high speed, and vary wavelengths. Accordingly, such OEO image modulators are used as a key component in a three-dimensional (3D) camera, a LADAR, and an IR imager.
OEO image modulators receive an optical image in near infrared (NIR)—IR wavelengths of about 800 nm to about 1700 nm, generate current due to photoelectric effect, amplify or modulate the current by applying a modulating signal so that the current has a desired waveform, such as a sine waveform, a ramp waveform, or a square waveform, and then supply the amplified or modulated current to a light emitting device such as a light emitting diode (LED). The light emitting device supplied with the current emits visible light with wavelengths of about 450 nm to about 650 nm to which the sensitivity of an imaging device, such as a CCD, is high.
Since a light receiving device and a light emitting device in such an OEO image modulator are close to each other, the risk of optical interference between the light receiving device and the light emitting device is very high. For example, optical information generated by the light emitting device is imaged by the CCD. However, part of light scattered in the light emitting device is absorbed by the light receiving device. The light absorbed by the light receiving device is emitted through photo-electric conversion. The emitted light is unnecessary and becomes noise, thereby acting as a noise component to a normal image output from the OEO image modulator. The noise component may degrade the quality and reliability of the normal image, and degrade the modulation efficiency of the OEO image modulator as well.